Great intro to DSP. If you're looking to build your EE library further, Ron Mancini's Op Amps for Everyone is also available as a free download from Texas Instruments. If you don't already have it, you can get it here: http://focus.ti.com/lit/an/slod006b/slod006b.pdf

Fantastic reference. I suggest you submit it as its own link.

Happy to upvote this, even though it's not new. I think this is the best introductory DSP text anyway, and I've got a bunch of them. Its treatment of the various approaches to the fourier transform (and more importantly, why they work) is outstanding.